To reduce the arrangement space of such electrical parts as an isolator in an electric power generation device that adopts a thyristor starting device and to simplify interlocking between switching devices.

A thyristor starting device 5 receives power from a power station common power supply 1 in a power station and supplies power to a generator 9 via a thyristor starting device output side isolator 2, thus operating the generator 9 as the electric motor but using a power station common power supply 1 when operating the thyristor starting device 5 as an excitation power supply, performing branching from the main circuit of the generator 9 via a transformer 6 for excitation at the time of generation operation, and at the same time, switching a power supply circuit from the power station common power supply 1 to the branch circuit of the main circuit of the generator 9 also for an excitation circuit. In the configuration of the generation device with this kind of thyristor starting device, a multiple-contact isolator 4 with isolator functions for two units is applied as an excitation circuit when operating the thyristor starting device and as a switching circuit of the excitation circuit when performing the generation operation of the generator, thus reducing electrical parts arrangement space and improving the reliability in an interlock.